Methods of etching metal-containing layers

ABSTRACT

A method of removing a metal-containing layer (e.g., tungsten) from a substrate is provided. The method includes generating a first plasma in a process volume of a plasma chamber when a patterned device is disposed on a substrate support in the process volume. The patterned device includes a patterned region and an unpatterned region; a substrate; a tungsten-containing layer formed over the substrate; a supporting layer disposed between the tungsten-containing layer and the substrate. The patterned region includes exposed surfaces of the supporting layer and the unpatterned region does not include any exposed surfaces of the supporting layer. The method further includes depositing a first film over the patterned region of the tungsten-containing layer with the first plasma; and removing portions of the unpatterned region of the tungsten-containing layer with the first plasma without depositing the first film over the unpatterned region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 62/564,257, filed Sep. 27, 2017, and U.S. provisional patentapplication Ser. No. 62/597,163, filed Dec. 11, 2017, which are bothhereby incorporated herein by reference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to methods forforming semiconductor device structures.

Description of the Related Art

Hard masks are used for etching deep, high aspect ratio (HAR) featuresthat conventional photoresists cannot withstand. As chip featurescontinue to shrink, innovations in hard masks are required to preservethe pattern integrity of tightly packed and/or tiny interconnectstructures. These innovations include using harder materials for thehard masks, such as metal-containing layers including tungsten,titanium, or tantalum, such as tungsten carbide (W_(x)C), tungstennitride (W_(x)N), tungsten silicide (W_(x)Si), tungsten boron carbide(W_(x)B_(y)C), tungsten oxide (WO_(x)), tungsten carbon nitride(W_(x)C_(y)N), titanium nitride, (TiN), titanium silicon nitride(Ti_(x)Si_(y)N), titanium oxide (TiO₂) Although metal-containing hardmasks, such as tungsten-containing hard masks can improve the process ofselectively etching features above the hard masks versus features belowthe hard mask, eventually portions or all of the hard masks need to beremoved. Selective removal of metal-containing hard masks, such astungsten-containing hard masks, has proved challenging, especially whenthere are substantial variations in the thickness of thetungsten-containing layer over different portions of thetungsten-containing layer.

Thus, there is a need for improved methods of selective removal ofmetal-containing layers, such as tungsten-containing layers.

SUMMARY

Embodiments of the present disclosure generally relate to methods forforming semiconductor device structures. In one embodiment, a method ofremoving a tungsten-containing layer from a substrate is provided. Themethod includes generating a first plasma in a process volume of aplasma chamber when a patterned device is disposed on a substratesupport in the process volume. The patterned device includes a patternedregion and an unpatterned region, a substrate, a tungsten-containinglayer formed over the substrate, a supporting layer disposed between thetungsten-containing layer and the substrate. The patterned regionincludes exposed surfaces of the supporting layer and the unpatternedregion does not include any exposed surfaces of the supporting layer.The method further includes depositing a first film over the patternedregion of the tungsten-containing layer with the first plasma, andremoving portions of the unpatterned region of the tungsten-containinglayer with the first plasma without depositing the first film over theunpatterned region.

In another embodiment, a method of removing a tungsten-containing layerfrom a substrate is provided. The method includes generating a firstplasma in a process volume of a plasma chamber, wherein a patterneddevice is disposed on a substrate support in the process volume. Thepatterned device includes a substrate; a tungsten-containing layerformed over the substrate, the tungsten-containing layer comprising apatterned region including changes in thickness of thetungsten-containing layer of at least 20% and an unpatterned regionwithout any changes in thickness greater than 10%. The method furtherincludes depositing a first film comprising tungsten over the patternedregion of the tungsten-containing layer with the first plasma, andremoving portions of the unpatterned region of the tungsten-containinglayer with the first plasma without depositing the first film over theunpatterned region.

In another embodiment, a method of removing a tungsten-containing layerfrom a substrate is provided. The method includes generating a firstplasma in a process volume of a plasma chamber, wherein a patterneddevice is disposed on a substrate support in the process volume. Thepatterned device includes a substrate, a tungsten-containing layercomprising tungsten and one or more of carbon and nitrogen formed overthe substrate, the tungsten-containing layer comprising a patternedregion including changes in thickness of the tungsten-containing layerof at least 20% and an unpatterned region without any changes inthickness greater than 10%; and a supporting layer comprising siliconnitride or silicon oxide disposed between the tungsten-containing layer.The method further includes depositing a first film comprising tungstenover the patterned region of the tungsten-containing layer with thefirst plasma; removing portions of the unpatterned region of thetungsten-containing layer with the first plasma without depositing thefirst film over the unpatterned region, generating a second plasma inthe process volume of the plasma chamber after generating the firstplasma, and removing the first film and portions of the patterned regionand the unpatterned region of the tungsten-containing layer with thesecond plasma, wherein an RF bias is supplied to the substrate supportat a first power level during the generation of the first plasma and theRF bias is supplied to the substrate support at a second power levelduring generation of the second plasma, wherein the first power level islower than the second power level.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1A is a partial cross-sectional view of a patterned device beforebeing treated using one or more of the methods described in the Figuresbelow.

FIG. 1B is a partial cross-sectional view of the patterned device ofFIG. 1A after being treated using one or more of the methods describedbelow in reference to FIGS. 3-6.

FIG. 2 is a simplified cutaway view for an exemplary etching processchamber for selectively removing a tungsten-containing layer from apatterned device, such as the tungsten-containing layer from thepatterned device described above in reference to FIG. 1A.

FIG. 3 is a process flow diagram of a method of forming the patterneddevice of FIG. 1B using the etching process chamber of FIG. 2, accordingto one embodiment.

FIGS. 4A-4D illustrate different stages of removing thetungsten-containing layer from the patterned device of FIG. 4A to formthe patterned device of FIG. 4D using the method 1000 of FIG. 3,according to one embodiment.

FIG. 5 is a process flow diagram of a method of forming the patterneddevice of FIG. 1B using the etching process chamber of FIG. 2, accordingto one embodiment.

FIGS. 6A-6D illustrate different stages of removing thetungsten-containing layer from the patterned device of FIG. 6A to formthe patterned device of FIG. 6D using the method of FIG. 5, according toone embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally relate to methods ofselective removal of metal-containing layers (e.g., tungsten-containinghard masks) using dry etching. The methods described below can be usedto selectively etch metal-containing layers, such as tungsten carbide(W_(x)C), titanium nitride (TiN), tungsten nitride (W_(x)N), tungstensilicide (W_(x)Si), tungsten Boron Carbide (W_(x)B_(y)C) and tungstencarbon nitride (W_(x)C_(y)N). For example, the methods described belowcan be used to remove tungsten-containing layers from patternedstructures without damaging the underlying layers even when there aresubstantial differences in thickness of the tungsten-containing layerover different portions of the patterned structure. Furthermore, themethods described below can selectively etch tungsten-containing layers(e.g., WC) relative to silicon oxide at a ratio of greater than 300:1and can selectively etch tungsten-containing layers (e.g., WC) relativeto silicon nitride at a ratio of greater than 1000:1. Although thefollowing disclosure generally describes methods of selective removal oftungsten-containing hard masks, the disclosure is equally applicable toselective removal of any layer formed of a carbide, oxide, or nitride,such as a carbide, oxide, or nitride including one or more metals, suchas a carbide, oxide, or nitride layer including one or more of tungsten,tantalum, titanium (e.g., TiN), cobalt, strontium (such as SrTiO_(x)),hafnium, in a semiconductor process.

FIG. 1A is a partial cross-sectional view of a patterned device 100before being treated using one or more of the methods described below.FIG. 1B is a partial cross-sectional view of the patterned device 100′after being treated using one or more of the methods described below inreference to FIGS. 3-6. Notably, in FIG. 1B, while all of thetungsten-containing layer 111 of FIG. 1A has been removed, none or onlya negligible amount of the underlying layer 112 has been removed. Beforebeing treated, patterned device 100 includes a tungsten-containing layer111 that has substantial variations in thickness over different portionsof the tungsten-containing layer 111. These thickness variations presentchallenges in removing the tungsten-containing layer without damagingthe underlying layer(s). For example, if conventional etching processeswere applied to remove the tungsten-containing layer 111 shown in FIG.1A, then portions of the layer 112 underlying thinner portions of thetungsten-containing layer 111 would be damaged (e.g., partially removed)in the process. The methods described below overcome these challenges byusing methods that can selectively etch the thicker portions of thetungsten-containing layer 111 at faster overall rates than the thinnerportions of the tungsten-containing layer 111. For example, the methodsdescribed below can include operations which etch the thicker portionswhile simultaneously depositing and protecting a film over the thinnerportions.

Referring to FIG. 1A, the patterned device 100 includes a substrate 50,the tungsten-containing layer 111, and a supporting layer 112. Thesupporting layer 112 is formed over the substrate 50, and thetungsten-containing layer 111 is formed on the supporting layer 112. Insome embodiments, the tungsten-containing layer 111 can be a hard masklayer. The tungsten-containing layer 111 can be formed of tungstencarbide (WC), tungsten carbon nitride (WCN), tungsten nitride (WN),tungsten silicide (WSi), tungsten boride (WB), or other layer includingtungsten. In some embodiments, the tungsten composition in thetungsten-containing layer 111 can be greater than 15%, such as greaterthan 60%, or greater than 80%. In some embodiments, the supporting layer112 is formed of a dielectric material, such as silicon nitride orsilicon oxide. For example, in some embodiments the supporting layer 112can be used as a part of capping layer for a conductive structure, suchas an interconnect that can be subsequently formed by, for examplepartially filling the holes or trenches 115 with a conductive material.

In some embodiments, an intermediate layer 113 is formed between thesupporting layer 112 and the substrate 50. The intermediate layer 113can include one or more individual layers (not shown), such as one ormore conductive and/or insulating layers.

The patterned device 100 includes a plurality of trenches 15 formed overthe substrate 50. Although the patterned device 100 is shown includingthe plurality of trenches 15, in other embodiments the patterned device100 can include other patterned features, such as other high aspectratio structures, for example, holes, line/space, vias or dual damascenestructures. In some embodiments, the high aspect ratio features have anaspect ratio greater than 1:1, such as greater than 2:1, such as greaterthan 50:1. The patterned device 100 includes a patterned region 101Athat includes the plurality of trenches 15. The patterned device 100further includes an unpatterned region 101B that does not includepatterned features, such as the plurality of trenches 15. The patternedregion 101A includes exposed surfaces of one or more underlying layers,such as the supporting layer 112. The unpatterned region 101B does notinclude any exposed surfaces of any underlying layers, such as thesupporting layer 112. Furthermore, the patterned region 101A can includechanges in thickness in the direction in which the layers are stacked(i.e., the Z-direction) of the tungsten-containing layer 111 of at least20% across the patterned region 101A (i.e., the XY plane) while theunpatterned region 101B does not include any changes in thickness of thetungsten-containing layer 111 in the Z-direction across the XY planegreater than 10%. For example, the thickness of the tungsten-containinglayer 111 across the XY plane in the patterned region 101A is a firstthickness above the supporting layer 112 and is reduced to zero in thetrenches 115, which is a change in thickness greater than 20%. Moreover,the tungsten-containing layer 111 in the unpatterned region 101B can besubstantially flat in some embodiments, which is a change in thicknessless than 10%. In other embodiments, the patterned region 101A can bedefined by changes in elevation of the outer surface (i.e., top surface)of the tungsten-containing layer 111 in the Z-direction, which aregreater than 20% of the thickness of the tungsten-containing layer 111in the Z-direction while the unpatterned region 101B does not includeany changes in elevation in the Z-direction of the tungsten-containinglayer 111 greater than 10%.

Referring to FIG. 1A, the tungsten-containing layer 111 is substantiallythicker in the unpatterned region 101B than in the patterned region 101Adue to previous processing. For example, the processing to form thetrenches 115 is focused in the patterned region 101A and results in apartial removal of the portions of the tungsten-containing layer 111over the supporting layer 112 in the patterned region 101A while thissame processing leaves the tungsten-containing layer 111 in theunpatterned region 101B largely unaffected resulting in the substantialthickness difference of the tungsten-containing layer 111 between thepatterned region 101A and the unpatterned region 101B. The methodsdescribed below overcome these challenges presented by this thicknessdifference by using methods that can etch the thicker portions of thetungsten-containing layer 111 in the unpatterned region 101B at fasteroverall rates than the thinner portions of the tungsten-containing layer111 in the patterned region 101A. As described below, the methods caninclude operations which etch the thicker portions of thetungsten-containing layer 111 in the unpatterned region 101B whilesimultaneously depositing a film over the thinner portions of thetungsten-containing layer 111 in the patterned region 101A.

FIG. 2 is a simplified cutaway view for an exemplary etching processchamber 200 for selectively removing a tungsten-containing layer from apatterned device, such as the tungsten-containing layer 111 from thepatterned device 100 described above in reference to FIG. 1A. Oneexample of the process chamber that may be adapted to benefit from thedisclosure is an AdvantEdge Mesa Etch or Sym3 Etch processing chamber,available from Applied Materials, Inc., located in Santa Clara, Calif.It is contemplated that other process chambers, including those fromother manufactures, may be adapted to practice embodiments of thedisclosure.

The etching process chamber 200 includes a chamber body 205 having aprocess volume 201 defined therein. The chamber body 205 has sidewalls212 and a bottom 218 which are coupled to an electrical ground 226. Thesidewalls 212 have a protective inner liner 215 to extend the timebetween maintenance cycles of the etching process chamber 200. Thedimensions of the chamber body 205 and related components of the etchingprocess chamber 200 are not limited and generally are proportionallylarger than the size of the patterned device 100 to be processedtherein.

The chamber body 205 supports a chamber lid assembly 210 to enclose theprocess volume 201. The chamber body 205 may be fabricated from aluminumor other suitable materials. An access port 213 is formed through thesidewalls 212 of the chamber body 205, facilitating the transfer of thepatterned device 100 into and out of the etching process chamber 200.

A pumping port 245 is formed through one or more of the sidewalls 212 ofthe chamber body 205 and is connected to the process volume 201. Apumping device (not shown) is coupled through the pumping port 245 tothe process volume 201 to evacuate and control the pressure therein. Thepressure may be controlled during processing between about 1 mTorr toabout 200 mTorr, such as from about 5 mTorr to about 50 mTorr, such asabout 10 mTorr. The temperature of the process volume 201 can bemaintained between about 0° C. to about 180° C., such as from about 25°C. to about 120° C.

A gas panel 260 is coupled by a gas line 267 to the chamber body 205 tosupply gases into the process volume 201. The gas panel 260 may includeone or more process gas sources 261, 262, 263 and may additionallyinclude a dilution gas source 264. Examples of process gases that may beprovided by the gas panel 260 include, but are not limited to ahalogen-containing gas (e.g., Cl₂ HBr, BCl₃, Br₂), a hydrogen-containinggas (e.g., CH₃F, CH₂F₂, CHF₃, HBr, CH₄, H₂), and an oxygen-containinggas (e.g., O₂, COS, SO₂). In one example, the process volume 201 of theprocess chamber 200 into which the process gases flow is between 90,000cc and 160,000 cc, such as about 125,000 cc.

Valves 266 control the flow of the process gases from the gas sources261, 262, 263, 264 from the gas panel 260 and are managed by acontroller 265. The flow of the gases supplied to the process volume 201from the gas panel 260 may include combinations of the gases.

The chamber lid assembly 210 may include a nozzle 214. The nozzle 214has one or more ports for introducing the process gases and inert gasesfrom the gas sources 261, 262, 263, 264 of the gas panel 260 into theprocess volume 201. After the process gases are introduced into theetching process chamber 200, the gases are energized to form plasma. Anantenna 248, such as one or more inductor coils, may be providedadjacent to the etching process chamber 200. An antenna power supply 242applies power to the antenna 248 through a match circuit 241 toinductively couple energy, such as RF energy, to the process gas tomaintain a plasma formed from the process gas in the process volume 201of the etching process chamber 200. The operation of the antenna powersupply 242 may be controlled by a controller, such as the controller265, that also controls the operation of other components in the etchingprocess chamber 200.

A substrate support pedestal 235 is disposed in the process chamber 200to support the patterned device 100 during processing. The substratesupport pedestal 235 may include an electro-static chuck 222 for holdingthe patterned device 100 during processing. The electro-static chuck(ESC) 222 uses electro-static attraction to hold the substrate 50 of thepatterned device 100 to the substrate support pedestal 235. The ESC 222includes an electrode 221 powered by a power source 250. The electrode221 is embedded in the ESC 222 within a dielectric body. The powersource 250 may also include a system controller for controlling theoperation of the electrode 221 by directing a DC current to theelectrode 221 for chucking and de-chucking the patterned device 100.

Furthermore, the electrode 221 may further be coupled to an RF powersupply 225 integrated with a match circuit 224. The RF power supply 225provides a bias to the electrode 221 which attracts plasma ions, formedby the process gases in the process volume 201, to the ESC 222 andpatterned device 100 positioned thereon. The ESC 222 has an isolator 228for the purpose of making the sidewall of the ESC 222 less attractive tothe plasma to prolong the maintenance life cycle of the ESC 222.Additionally, the substrate support pedestal 235 may have a cathodeliner 236 to protect the sidewalls of the substrate support pedestal 235from the plasma gases and to extend the time between maintenance of theetching process chamber 200.

The ESC 222 may include heaters (not shown) disposed therein andconnected to a power source (not shown), for heating the patterneddevice 100, while a heat transfer base 229 supporting the ESC 222 mayinclude conduits for circulating a heat transfer fluid to maintain atemperature of the ESC 222 and patterned device 100 disposed thereon.The ESC 222 is configured to perform in the temperature range requiredby the thermal budget of the device being fabricated on the patterneddevice 100. For example, the ESC 222 may be configured to maintain thepatterned device 100 at a temperature of about minus about 0 degreesCelsius to about 200 degrees Celsius for certain embodiments.

A cover ring 230 is disposed on the ESC 222 and along the periphery ofthe substrate support pedestal 235. The cover ring 230 is configured toconfine etching gases to a desired portion of the exposed top surface ofthe patterned device 100, while shielding the top surface of thesubstrate support pedestal 235 from the plasma environment inside theetching process chamber 200. Lift pins (not shown) are selectively movedthrough the substrate support pedestal 235 to lift the patterned device100 above the substrate support pedestal 235 to facilitate access to thepatterned device 100 by a transfer robot (not shown) or other suitabletransfer mechanism.

The controller 265 may be utilized to control the process sequence,regulating the gas flows from the gas panel 260 into the etching processchamber 200 and other process parameters, such as the frequencies andpower provided to the electrode 221 and the antennas 248. Softwareroutines, when executed by a CPU of the controller 265, transform theCPU into a specific purpose computer (controller) that controls theetching process chamber 200 such that the processes are performed. Thesoftware routines may also be stored and/or executed by a secondcontroller (not shown).

FIG. 3 is a process flow diagram of a method 1000 of forming thepatterned device 100′ of FIG. 1B using the etching process chamber 200of FIG. 2, according to one embodiment. FIGS. 4A-4D illustrate differentstages of removing the tungsten-containing layer 111 from the patterneddevice 100 of FIG. 4A to form the patterned device 100′ of FIG. 4D usingthe method 1000 of FIG. 3, according to one embodiment. FIGS. 4A and 4Dare the same as FIGS. 1A and 1B described above. Referring to FIGS. 2, 3and 4A-4D, the method 1000 is described.

At block 1002, process gases and an optional dilution gas (e.g., Ar, He,N₂) are supplied to the process volume 201 of the process chamber 200.In one embodiment, a first gas comprising oxygen (e.g., O₂, COS, SO₂), asecond gas comprising halogen-containing gases such aschlorine-containing gas (e.g., BCl₃ Cl₂) or a bromine-containing gas(e.g., HBr, Br2) are provided to the process volume 201 of the processchamber 200. In another embodiment, the first gas comprising oxygen, thesecond gas comprising chlorine, and a third gas comprising hydrogen(e.g., CH₄, H₂) are provided to the process volume 201 of the processchamber 200. The chlorine-containing gas can be provided to the processvolume 201 at a flowrate from about 0 to about 2000 sccm, such as fromabout 50 sccm to about 1000 sccm. The oxygen-containing gas can beprovided to the process volume 201 at a flowrate from about 0 to about1000 sccm, such as from about 10 sccm to about 200 sccm. Thehydrogen-containing gas can be provided to the process volume 201 at aflowrate from about 0 to about 250 sccm, such as from about 5 sccm toabout 100 sccm. The dilution gas can be provided to the process volume201 at a flowrate from about 0 to about 1000 sccm, such as from about100 sccm to about 500 sccm.

At block 1004, a first plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated. The first plasma canbe generated by energizing the antenna 248 with energy, such as RFenergy. The antenna power supply 242 can supply RF energy at frequenciesfrom about 0.1 MHz to about 200 MHz, such as from about 0.3 MHz to about40 MHz, or even from about 0.3 MHz to about 13.56 MHz, such as about 2MHz at power levels from about 250 W to about 9000 W, such as from about500 W to about 4500 W, such as about 2000 W. The RF energy supplied tothe antenna 248 can be pulsed at a duty cycle from about 10% or higher,and in some embodiments continuous wave RF energy is applied to theantennas 248. In some embodiments, the duty cycle of the pulse is fromabout 25% to about 95%. However, in other embodiments continuous wave RFenergy can be applied to the antennas 248.

Additionally, at block 1004, a bias signal can be applied to theelectrode 221 of the electrostatic chuck 222. The bias signal from theelectrode 221 can be used to fine tune the plasma and control whetherthe plasma results in etching portions of the tungsten-containing layer111 and/or depositing additional material over portions of thetungsten-containing layer 111. The RF power supply 225 may provide RFpower to the electrode 221 at a power level from about 25 W to about1000 W, such as from about 75 W to about 500 W. The RF power supply 225can supply RF energy at frequencies from about 0.1 MHz to about 200 MHz,such as from about 0.2 MHz to about 60 MHz, or even from about 0.2 MHzto about 13.56 MHz, such as about 2 MHz. The RF power supply 225provides a bias to the electrode 221 which attracts plasma ions, formedby the process gases in the process volume 201, to the ESC 222 andpatterned device 100 positioned thereon. The RF power supply 225 maycycle on and off, or pulse, during processing of the patterned device100.

For example, in one embodiment, the RF energy supplied by RF powersupply 225 can be pulsed at a duty cycle from about 10% to about 98%,such as from about 25% to about 95%. In another embodiment, continuouswave RF energy is provided by the RF power supply 225. In someembodiments, the duty cycle can be in synchronous pulsing for the source(i.e., the antenna power supply 242) and the bias (i.e., the RF powersupply 225). In other embodiments, advanced pulsing methods such as adelay between pulsing of the source and the bias can be used. In suchembodiments, the source can pulse at a different or same duty cycle asthe bias, and the bias pulse can be applied with a delay relative to thesource. In some embodiments, when the source duty cycle is in the ONphase, the bias duty cycle is in the OFF phase, and when bias duty cycleis in the ON phase, the source duty cycle is in the OFF phase.

Referring to FIGS. 3 and 4B, at block 1006, a first film 116 isdeposited over the patterned region 101A of the tungsten-containinglayer 111 with the first plasma. The first film 116 can include tungsten(e.g., tungsten oxide). In some embodiments, the first film 116 can havea thickness from about 30 nm to about 200 nm, such as about 100 nm. Insome embodiments, the first film 116 can completely cover the trenches115 creating voids 117. The voids 117 can be beneficial when the etchrate of a plasma for the supporting layer 112 is higher than desired.For example, once the voids 117 are formed a plasma that is aggressivetowards etching the tungsten-containing layer 111 in the unpatternedregion can be applied with less concern for etching the supporting layer112 while the voids 117 are still covered and thus protected by thefirst film 116. Thus, in some embodiments the first plasma can bemodified (e.g., modifying flowrates of gases and/or electricalcharacteristics of energy provided to antenna 248 and/or to theelectrode 221) once the voids 117 are formed to take advantage of theprotection of the supporting layer 112 provided by the first film 116.In some embodiments, tungsten oxide is the only nonvolatile byproductgenerated from exposing the tungsten-containing layer 111 to the firstplasma. Volatile byproducts can include carbon monoxide as well as gasesincluding chlorine and one or more compounds of tungsten and oxygen.

Also at block 1006, portions of the tungsten-containing layer 111 in theunpatterned region 101B are removed with the first plasma. At thecompletion of block 1006, the thickness of the tungsten-containing layer111 in the unpatterned region 101B is substantially reduced while thethickness of the tungsten-containing layer 111 in the patterned region101A is not reduced as shown in FIG. 4B. Thus, a difference of thethickness of the tungsten-containing layer 111 between the patternedregion 101A and the unpatterned region 101B is substantially reduced byexecution of block 1006. In some embodiments, at block 1006, thethickness of the tungsten-containing layer 111 in the patterned region101A is reduced, but by a substantially smaller amount than thethickness of the tungsten-containing layer 111 of the unpatterned region101B. For example, the thickness reduction of the tungsten-containinglayer 111 in the unpatterned region 101B can be at least two timesgreater than the thickness reduction of the tungsten-containing layer111 found in the patterned region 101A, such as at least ten timesgreater. Thus, the etching process at block 1006 is highly selectivebetween the unpatterned region 101B (etching) and the patterned area110A (deposition). Notably, the first film 116 is not deposited over theunpatterned region 101B of the tungsten-containing layer 111.

At block 1008, a second plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated after generating thefirst plasma. The second plasma can be generated by energizing theantenna 248 with energy, such as RF energy. Additionally, at block 1008,a bias signal can be applied to the electrode 221 of the electrostaticchuck 222. The bias signal from the electrode 221 can be used to finetune the plasma and control whether the plasma results in etchingportions of the tungsten-containing layer 111 and/or depositingadditional material over portions of the tungsten-containing layer 111.The second plasma is generated using different gases (e.g., differentflowrates or different gas sources) and/or different electricalcharacteristics (e.g., power level, frequency, continuous wave, pulse,duty cycle of pulse) of the power provided to the antenna 248 and/or theelectrode 221.

Referring to FIGS. 3 and 4C, at block 1010, the first film 116 isremoved with the second plasma. Furthermore, at block 1010 portions ofthe patterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 are removed with the second plasma. At thecompletion of block 1010, a difference in thickness between thepatterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 is substantially reduced relative to theinitial difference in thickness between the patterned region 101A andthe unpatterned region 101B of the tungsten-containing layer 111 at thestart of method 1000.

As mentioned above, the gases provided to the process volume 201 of theprocess chamber 200 for the second plasma can be different gases ordifferent flowrates of gases relative to the gases and flowratesprovided to the process volume 201 of the process chamber 200 for thefirst plasma. For example, in one embodiment of method 1000, an additionof 5 sccm of methane during the second plasma can be sufficient to stopdeposition of the first film 116 over the patterned region 101A of thetungsten-containing layer 111 and instead cause removal of the firstfilm 116 as well as causing the removal of portions of the patternedregion 101A and the unpatterned region 101B of the tungsten-containinglayer 111 relative to a first plasma not including any methane. Thedifferences in the process conditions between the first plasma and thesecond plasma for this example are shown below in Table 1. In anotherembodiment, an optional second plasma can be formed by decreasing theflowrate of oxygen to 15 sccm from the 25 sccm in the first plasma whileall other flowrates and other conditions can remain the same as thoseshown below for the first plasma in Table 1. This decrease in theflowrate of oxygen without any addition of methane is also sufficient tostop deposition of the first film 116 over the patterned region 101A ofthe tungsten-containing layer 111 and instead cause removal of the firstfilm 116 as well as causing the removal of portions of the patternedregion 101A and the unpatterned region 101B of the tungsten-containinglayer 111.

In yet another embodiment, the transition between the first plasma andthe second plasma can be accomplished by changing the bias power appliedto the electrode 221 while keeping other process conditions constant.For example, an alternate first plasma can be generated by supplyingoxygen, chlorine, and methane to the process volume with a bias power of125 W, and an alternate second plasma can be generated by supplying thesame gases at the same flowrates but at a bias power or 150 W as shownbelow in Table 1.

TABLE 1 Pressure Power (W) to Bias Power (W) to Bias Duty O₂ Cl₂ CH₄mTorr Antenna 248 electrode 221 Cycle sccm sccm sccm First Plasma 102000 175 75% 25 200 0 Second Plasma 10 2000 175 75% 25 200 5 Optional 102000 175 75% 15 200 0 Second Plasma Alternate 10 2000 125 75% 25 200 5First Plasma Alternate 10 2000 150 75% 25 200 5 Second Plasma

Furthermore, as mentioned above the electrical characteristics for thepower provided to the antenna 248 and/or for the power provided to theelectrode 221 may be different at block 1008 for generating the secondplasma relative to block 1004 for generating the first plasma. Forexample, in one embodiment of method 1000, an increase in the bias powerprovided to the electrode 221 from about 125 W to about 150 W can besufficient to stop deposition of the first film 116 over the patternedregion 101A of the tungsten-containing layer 111 and instead causeremoval of the first film 116 as well as causing the removal of portionsof the patterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111. The differences in the process conditionsbetween the first plasma and the second plasma for this example areshown below in Table 2.

TABLE 2 Pressure Power (W) to Bias Power (W) to Bias Duty O₂ Cl₂ CH₄mTorr Antenna 248 electrode 221 Cycle sccm sccm sccm First Plasma 102000 125 75% 25 200 5 Second Plasma 10 2000 150 75% 25 200 5

At block 1012, a third plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated after generating thesecond plasma. In some embodiments, the gases provided to the processvolume 201 of the process chamber 200 for the third plasma are differentgases or different flowrates of gases relative to the gases andflowrates provided to the process volume 201 of the process chamber 200for the first plasma and second plasma. Furthermore, the electricalcharacteristics for the power provided to the antenna 248 and/or for thepower provided to the electrode 221 may be different at block 1012 forgenerating the third plasma relative to block 1004 for generating thefirst plasma and relative to block 1008 for generating the secondplasma. In one example, the process conditions for the third plasma areshown below in Table 3. In this example, the gases provided to theprocess volume 201 of the process chamber 200 include a gas compositionthat includes an oxygen containing gas (e.g., O₂) and a halogencontaining gas (e.g., molecular chlorine (Cl₂)), and no hydrogen orcarbon containing gases (e.g., CH₄, HBr).

TABLE 3 Pressure Power (W) to Bias Power of 2 MHz(W) Bias Duty O₂ Cl₂CH₄ mTorr Antenna 248 to electrode 221 Cycle sccm sccm sccm Third Plasma10 2000 100 75% 30 200 0

Referring to FIGS. 3 and 4D, at block 1014, remaining portions of thepatterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 are removed with the third plasma toexpose a top surface of the supporting layer 112 (i.e., the surfacepreviously covered by the tungsten-containing layer 111). Because theremaining portions of the tungsten-containing layer 111 can be removedwith the third plasma, the third plasma can be highly selective toremoving the tungsten-containing layer 111 relative to the underlyingsupporting layer 112, such as being more selective than the first plasmaor the second plasma described above. In one embodiment, a highlyselective etching process for removing the tungsten-containing layer 111relative to the underlying supporting layer 112 (e.g., silicon nitrideor silicon oxide) at ratios greater than 300:1 can be achieved by aprocess that includes applying RF power to the electrode 221 at afrequency from about 0.2 MHz to about 5 MHz, such as about 2 MHz at abias power level from about 75 W to about 125 W, such as at about 100 W.In some embodiments, a pulsed (e.g., a duty cycle of 75%) or continuouswave RF energy can be applied to the antennas 248 at block 1014. At thecompletion of block 1014, the tungsten-containing layer 111 can be fullyremoved to form the patterned device 100′ without removing and/ordamaging any underlying layers, such as supporting layer 112. In someembodiments, a negligible amount of an underlying layer, such as thesupporting layer 112, is removed in one or more of the patterned region101A and/or the unpatterned region 101B. For example, a thickness of thesupporting layer 112 after generation of the third plasma within 0.5% ofthe thickness of the supporting layer 112 before generation of the firstplasma is considered a negligible amount. The process conditions for thethird plasma can be selected to selectively remove thetungsten-containing layer 111 (e.g., WC) relative to the supportinglayer 112 (e.g., silicon oxide) at ratio is greater than 100:1, such asgreater than 300:1, such as even greater than 1000:1.

FIG. 5 is a process flow diagram of a method 2000 of forming thepatterned device 100′ of FIG. 1B using the etching process chamber 200of FIG. 2, according to one embodiment. FIGS. 6A-6D illustrate differentstages of removing the tungsten-containing layer 111 from the patterneddevice 100 of FIG. 6A to form the patterned device 100′ of FIG. 6D usingthe method 2000 of FIG. 5, according to one embodiment. FIGS. 6A and 6Dare the same as FIGS. 1A and 1B described above. Referring to FIGS. 2, 5and 6A-6D, the method 2000 is described.

At block 2002, process gases and an optional dilution gas (e.g., Ar, He,N₂) are supplied to the process volume 201 of the process chamber 200.In one embodiment, a first gas comprising oxygen (e.g., O₂, COS, SO₂), asecond gas comprising chlorine (e.g., Cl₂) are provided to the processvolume 201 of the process chamber 200. In another embodiment, the firstgas comprising oxygen, the second gas comprising chlorine, and a thirdgas comprising hydrogen (e.g., CH₄, H₂) are provided to the processvolume 201 of the process chamber 200. The gases provided and theflowrates for the gases at block 2002 can be the same as described abovefor block 1002 of FIG. 3 or the same as those shown above in Tables 1and 2 for the first plasma.

At block 2004, a first plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated. The first plasma canbe generated by energizing the antenna 248 with energy, such as RFenergy. The antenna power supply 242 can supply RF energy to the antenna248 with the same electrical characteristics described above for block1004 of FIG. 3 or shown above in Tables 1 and 2 for the first plasma.

Additionally, at block 2004, a bias signal can be applied to theelectrode 221 of the electrostatic chuck 222. The bias signal from theelectrode 221 can be used to fine tune the plasma and control whetherthe plasma results in etching portions of the tungsten-containing layer111 and/or depositing additional material over portions of thetungsten-containing layer 111. The RF power supply 225 may provide RFpower to the electrode 221 with the same electrical characteristicsdescribed above for block 1004 of FIG. 3 or shown above in Tables 1 and2 for the first plasma.

Referring to FIGS. 5 and 6B, at block 2006, the first film 116 isdeposited over the patterned region 101A of the tungsten-containinglayer 111 with the first plasma. The first film 116 can include tungsten(e.g., tungsten oxide). In some embodiments, tungsten oxide is the onlynonvolatile byproduct generated from exposing the tungsten-containinglayer 111 to the first plasma. Volatile byproducts can include carbonmonoxide as well as gases including chlorine and one or more of tungstenand an oxygen. Also at block 1006, portions of the tungsten-containinglayer 111 in the unpatterned region 101B are removed with the firstplasma.

At the completion of block 2006, the first film 116 does not completelycover the trenches 115 in block 2006, and thus the voids 117 describedabove in reference to block 1006 are not formed in block 2006. Also,less material is removed from the tungsten-containing layer 111 in theunpatterned region 101B in block 2006 relative to block 1006. In someembodiments, the reduced deposition of the first film and the reducedremoval of the tungsten-containing layer 111 in the unpatterned region101B in block 2006 relative to block 1006 is due to a shorter durationof block 2006 relative to block 1006.

Also at the completion of block 2006, the thickness of thetungsten-containing layer 111 in the unpatterned region 101B issubstantially reduced while the thickness of the tungsten-containinglayer 111 in the patterned region 101A is not reduced as shown in FIG.4B. Thus, a difference of the thickness of the tungsten-containing layer111 between the patterned region 101A and the unpatterned region 101B issubstantially reduced by execution of block 2006. In some embodiments,at block 2006, the thickness of the tungsten-containing layer 111 in thepatterned region 101A is reduced, but by a substantially smaller amountthan the thickness of the tungsten-containing layer 111 of theunpatterned region 101B. Notably, the first film 116 is not depositedover the unpatterned region 101B of the tungsten-containing layer 111.

At block 2008, a second plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated after generating thefirst plasma. The second plasma can be generated by energizing theantenna 248 with energy, such as RF energy. Additionally, at block 2008,a bias signal can be applied to the electrode 221 of the electrostaticchuck 222. The bias signal from the electrode 221 can be used to finetune the plasma and control whether the plasma results in etchingportions of the tungsten-containing layer 111 and/or depositingadditional material over portions of the tungsten-containing layer 111.The second plasma is generated using different gases (e.g., differentflowrates or different gas sources) and/or different electricalcharacteristics (e.g., power level, frequency, continuous wave, pulse,duty cycle of pulse) of the power provided to the antenna 248 and/or theelectrode 221. The second plasma generated in block 2008 can begenerated using the same process conditions as those described above forthe second plasma generated in block 1008 of FIG. 3. Exemplary processconditions to form the second plasma can also be found above in Tables 1and 2 for the second plasma.

Referring to FIGS. 5 and 6C, at block 2010, the first film 116 isremoved with the second plasma. Furthermore, at block 2010 portions ofthe patterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 are removed with the second plasma. At thecompletion of block 2010, a difference in thickness between thepatterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 is substantially reduced relative to theinitial difference in thickness between the patterned region 101A andthe unpatterned region 101B of the tungsten-containing layer 111 at thestart of method 1000. However, at the first completion of block 2010,there is more remaining material in the tungsten-containing layer 111 ofthe patterned region 101A and the unpatterned region 101B relative tothe completion of block 1010 of FIG. 3. To remove this additionalmaterial, blocks 2004 to 2010 (see FIGS. 6B and 6C) are repeated one ormore times, such as between 1 and about 20 times, such as about 10times. In some embodiments, the reduced removal of thetungsten-containing layer 111 of the patterned region 101A and theunpatterned region 101B in block 2006 relative to block 1006 is due to ashorter duration of block 2010 relative to block 1010.

At block 2011, a determination is made as to whether a desired thicknessof the tungsten-containing layer 111 in the patterned region 101A and/orthe unpatterned region 101B has been reached by the removal of portionsof the tungsten-containing layer 111 in blocks 2004-2010. If the desiredthickness has not been reached, then blocks 2004-2010 can be repeated insuccession to remove additional material from the tungsten-containinglayer 111. If the desired thickness has been reached, then a thirdplasma can be generated to remove the remaining portions of thetungsten-containing layer 111 in the patterned region 101A and theunpatterned region 101B. Using a repetitive process of blocks 2004-2010to incrementally remove portions of the tungsten-containing layer 111,for example by using multiple shorter durations of blocks 2004-2010performed in a cyclic fashion, as opposed to executing 2004-2010 once(i.e., the process used in method 1000 of FIG. 3), to remove acomparable overall portion of the tungsten-containing layer 111, canhelp to reduce particle generation in the process volume 201. Forexample, removing 100 nm or more of the tungsten-containing layer withone execution of blocks 2004-2010 (i.e., in one cycle) can causeparticle generation and/or damage the device 100 being processed due tothe extended length of the processing blocks. Furthermore, using therepetitive process with shorter durations for the first plasma can helpreduce the variations in the profile, properties and/or composition ofthe first film 116 across the patterned region 101A, which can helppromote achieving more uniform and consistent results at the end of themethod 2000 for forming the patterned device 100′.

At block 2012, a third plasma of the gases provided to the processvolume 201 of the process chamber 200 is generated after generating thesecond plasma. In some embodiments, the gases provided to the processvolume 201 of the process chamber 200 for the third plasma are differentgases or different flowrates of gases relative to the gases andflowrates provided to the process volume 201 of the process chamber 200for the first plasma and second plasma. Furthermore, the electricalcharacteristics for the power provided to the antenna 248 and/or for thepower provided to the electrode 221 may be different at block 2012 forgenerating the third plasma relative to block 2004 for generating thefirst plasma and relative to block 2008 for generating the secondplasma. The third plasma generated in block 2012 can be generated usingthe same process conditions as those described above for the thirdplasma generated in block 1012 of FIG. 3. Exemplary process conditionsto form the second plasma can also be found above in Table 3.

Referring to FIGS. 5 and 6D, at block 2014, remaining portions of thepatterned region 101A and the unpatterned region 101B of thetungsten-containing layer 111 are removed with the third plasma toexpose a top surface of the supporting layer 112 (i.e., the surfacepreviously covered by the tungsten-containing layer 111). At thecompletion of block 2014, the tungsten-containing layer 111 can be fullyremoved to form the patterned device 100′ of FIG. 6D without removingand/or damaging any underlying layers, such as supporting layer 112. Insome embodiments, a negligible amount of an underlying layer, such asthe supporting layer 112, is removed in one or more of the patternedregion 101A and/or the unpatterned region 101B. For example, a thicknessof the supporting layer 112 after generation of the third plasma within0.5% of the thickness of the supporting layer 112 before generation ofthe first plasma is considered a negligible amount. The processconditions for the third plasma can be selected to selectively removethe tungsten-containing layer 111 (e.g., WC) relative to the supportinglayer 112 (e.g., silicon oxide) at ratio is greater than 100:1, such asgreater than 300:1, such as even greater than 1000:1.

Overall, the methods described above provide solutions to overcoming theproblem presented by removing a tungsten-containing layer disposed overa patterned device when the thickness of the tungsten-containing layervaries between a patterned region and an unpatterned region of thepatterned device. These problems are overcome by (1) generating a firstplasma to deposit a film over the patterned region of thetungsten-containing layer in the patterned region while removingportions of the tungsten-containing layer in the unpatterned region,followed by (2) generating a second plasma to remove the deposited filmwhile also removing portions of the tungsten-containing layer in thepatterned region and the unpatterned region that significantly reducesthe initial thickness variation of the tungsten-containing layer betweenthe patterned region and the unpatterned region, followed by (3)generating a third plasma to remove the remaining portions of thetungsten-containing layer in both the patterned region and theunpatterned region without any removal or damage to any underlyinglayers.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A method of removing a tungsten-containinglayer from a substrate, comprising: generating a first plasma in aprocess volume of a plasma chamber, wherein a patterned device isdisposed on a substrate support in the process volume, the patterneddevice comprising: a patterned region and an unpatterned region; asubstrate; a tungsten-containing layer formed over the substrate; and asupporting layer disposed between the tungsten-containing layer and thesubstrate, wherein the patterned region includes exposed surfaces of thesupporting layer and the unpatterned region does not include any exposedsurfaces of the supporting layer; depositing a first film over thepatterned region of the tungsten-containing layer with the first plasma;and removing portions of the unpatterned region of thetungsten-containing layer with the first plasma without depositing thefirst film over the unpatterned region.
 2. The method of claim 1,wherein the patterned region includes a plurality of high aspect ratiofeatures having an aspect ratio of at least 2:1.
 3. The method of claim2, wherein the unpatterned region is substantially flat.
 4. The methodof claim 1, wherein a thickness of the unpatterned region of thetungsten-containing layer is greater than a thickness of the patternedregion of the tungsten-containing layer before generation of the firstplasma.
 5. The method of claim 1, further comprising: generating asecond plasma in the process volume of the plasma chamber aftergenerating the first plasma; and removing the first film and portions ofthe patterned region and the unpatterned region of thetungsten-containing layer with the second plasma.
 6. The method of claim5, wherein a difference in thickness between the unpatterned region andthe patterned region after the generation of the second plasma is lessthan a difference in the thickness between unpatterned region and thepatterned region before the generation of the first plasma.
 7. Themethod of claim 5, further comprising: generating a third plasma in theprocess volume of the plasma chamber after generating the second plasma;and removing remaining portions of the patterned region and theunpatterned region of the tungsten-containing layer with the thirdplasma to expose a top surface of the supporting layer.
 8. The method ofclaim 7, wherein the supporting layer comprises silicon nitride orsilicon oxide.
 9. The method of claim 7, wherein a thickness of thesupporting layer after generation of the third plasma is within 0.5% ofthe thickness of the supporting layer before generation of the firstplasma.
 10. The method of claim 5, further comprising repeating thegeneration of the first plasma and the second plasma in succession aftera first generation of the second plasma; removing additional portions ofthe unpatterned region of the tungsten-containing layer with therepeated first plasma; and removing additional portions of the patternedregion and the unpatterned region of the tungsten-containing layer withthe repeated second plasma.
 11. The method of claim 7, furthercomprising repeating the generation of the first plasma and the secondplasma in succession after a first generation of the second plasma andbefore generation of the third plasma; removing additional portions ofthe unpatterned region of the tungsten-containing layer with therepeated first plasma; and removing additional portions of the patternedregion and the unpatterned region of the tungsten-containing layer withthe repeated second plasma.
 12. The method of claim 1, wherein the firstfilm includes tungsten.
 13. A method of removing a tungsten-containinglayer from a substrate, comprising: generating a first plasma in aprocess volume of a plasma chamber, wherein a patterned device isdisposed on a substrate support in the process volume, the patterneddevice comprising: a substrate; and a tungsten-containing layer formedover the substrate, the tungsten-containing layer comprising a patternedregion including changes in thickness of the tungsten-containing layerof at least 20% and an unpatterned region without any changes inthickness greater than 10%; depositing a first film comprising tungstenover the patterned region of the tungsten-containing layer with thefirst plasma; and removing portions of the unpatterned region of thetungsten-containing layer with the first plasma without depositing thefirst film over the unpatterned region.
 14. The method of claim 13,further comprising supplying a first gas comprising oxygen, a second gascomprising chlorine, and a third gas comprising hydrogen to the processvolume of the plasma chamber, wherein the first plasma comprises aplasma of the first gas, the second gas, and the third gas.
 15. Themethod of claim 14, wherein the first film comprises tungsten oxide. 16.The method of claim 13, wherein the tungsten-containing layer comprisestungsten carbide, tungsten carbon nitride, or tungsten nitride.
 17. Themethod of claim 13, further comprising: generating a second plasma inthe process volume of the plasma chamber after generating the firstplasma; and removing the first film and portions of the patterned regionand the unpatterned region of the tungsten-containing layer with thesecond plasma.
 18. The method of claim 17, wherein an RF bias issupplied to the substrate support at a first power level during thegeneration of the first plasma and the RF bias is supplied to thesubstrate support at a second power level during generation of thesecond plasma, wherein the first power level is different from thesecond power level.
 19. The method of claim 17, further comprising:generating a third plasma in the process volume of the plasma chamberafter generating the second plasma; and removing remaining portions ofthe patterned region and the unpatterned region of thetungsten-containing layer with the third plasma to expose a top surfaceof a supporting layer disposed over the substrate.
 20. A method ofremoving a tungsten-containing layer from a substrate, comprising:generating a first plasma in a process volume of a plasma chamber,wherein a patterned device is disposed on a substrate support in theprocess volume, the patterned device comprising: a substrate; atungsten-containing layer comprising tungsten and one or more of carbonand nitrogen formed over the substrate, the tungsten-containing layercomprising a patterned region including changes in thickness of thetungsten-containing layer of at least 20% and an unpatterned regionwithout any changes in thickness greater than 10%; and a supportinglayer comprising silicon nitride or silicon oxide disposed between thetungsten-containing layer and the substrate; depositing a first filmcomprising tungsten over the patterned region of the tungsten-containinglayer with the first plasma; removing portions of the unpatterned regionof the tungsten-containing layer with the first plasma withoutdepositing the first film over the unpatterned region; generating asecond plasma in the process volume of the plasma chamber aftergenerating the first plasma; and removing the first film and portions ofthe patterned region and the unpatterned region of thetungsten-containing layer with the second plasma, wherein an RF bias issupplied to the substrate support at a first power level during thegeneration of the first plasma and the RF bias is supplied to thesubstrate support at a second power level during generation of thesecond plasma, wherein the first power level is lower than the secondpower level.